JPH0742850Y2 - Front and rear wheel rotation absorber for four-wheel drive vehicle - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> In the present invention, in a four-wheel drive vehicle, when there is a difference in rotation speed between the front wheel and the rear wheel, the difference in rotation speed The present invention relates to a front and rear wheel rotation absorbing device for a four-wheel drive vehicle, which obtains a differential limiting torque according to a rotational difference.

<Prior art> A front and rear wheel rotation absorbing device of a conventional four-wheel drive vehicle, particularly a four-wheel drive vehicle without a center differential, includes a part of a power transmission system, that is, a propeller shaft or a drive pinion of a final reduction gear. There is one with a viscous coupling. This device uses viscous coupling to generate viscous friction torque (so-called differential limiting torque) that is almost proportional to the rotation difference between the front and rear wheels. It prevents the ringing phenomenon and eliminates the rotation difference at the time of high rotation to transmit power.

A front and rear wheel rotation absorbing device using a viscous coupling is disclosed in, for example, Japanese Utility Model Laid-Open No. 62-125616. The four-wheel drive vehicle of this publication has a viscous coupling on one of the left and right wheels.
Although the position where the viscous coupling is provided is different, similarly to the above, the viscous friction torque of the viscous coupling serves to absorb the rotation difference between the front and rear wheels and to transmit the power.

<Problems to be Solved by the Invention> In the above-described conventional front and rear wheel rotation absorbing device, in order to obtain a large differential limiting torque, the number of friction surfaces of the viscous coupling is increased, the filling rate of the viscous fluid and the Although it is necessary to increase the viscosity, there is a problem that the viscous coupling itself must be increased in size.

Further, according to the differential limiting characteristic by the viscous coupling of the conventional device, the relationship between the rotation difference between the front and rear wheels and the differential limiting torque is almost proportional, but more specifically,
It is in the relationship of drawing a parabola as shown in the figure. That is, when the difference in rotation between the front and rear wheels is small, the viscous coupling causes a significant increase in the differential limiting torque with a slight increase in the difference in rotation, and conversely, when the difference in rotation between the front and rear wheels is large, the rotation is limited. The range of increase in the differential limiting torque becomes smaller as the difference increases.

However, due to the demands of four-wheel drive vehicles (also called vehicles), when the rotation difference between the front and rear wheels is smaller than a certain rotational speed, the differential limiting torque is reduced to suppress the tight corner braking phenomenon well, It can be said that it is desirable to increase the differential limiting torque and transmit a large driving force when the rotational difference is greater than a certain rotational speed.

However, in the above-described conventional device, when the rotation difference between the front and rear wheels is small, the differential limiting torque is significantly increased by only slightly increasing the rotation difference, so that the rotation difference between the front and rear wheels is not sufficiently absorbed, and the tight corner brakes are not sufficiently absorbed. Cannot suppress the ringing phenomenon. On the contrary, when the rotation difference between the front and rear wheels increases, the increase in the differential limiting torque due to the increase in the rotation difference decreases, so the rotation of the front and rear wheels is insufficiently restrained and a large driving force cannot be transmitted. Absent. Therefore, there remains dissatisfaction in satisfying both the suppression of the tight corner braking phenomenon corresponding to the rotation difference between the front and rear wheels due to the demand of the vehicle and the transmission of a large driving force.

Therefore, in view of the above-mentioned problems in the conventional technology, an object of the present invention is to provide a four-wheeled vehicle that can satisfy both the suppression of the tight corner braking phenomenon adapted to the requirements of the vehicle and the transmission of a large driving force. An object is to provide a front and rear wheel rotation absorbing device for a driving vehicle.

<Means for Solving Problems> The present invention, which has a technical problem of solving the problems in the above-described conventional technology, is interposed in a part of a power transmission system of front and rear wheels of a four-wheel drive vehicle, A front and rear wheel rotation absorbing device for a four-wheel drive vehicle, which absorbs a difference in rotation between a front wheel and a rear wheel, wherein the device is provided between a driving side member and a driven side member of the power transmission system and is provided with an axial pressing force. Accordingly, a friction clutch that generates a differential limiting torque that limits the differential between the two members, and one of the driving side member and the driven side member movably provided in the axial direction, and the friction clutch has a shaft. A clutch pressing member that applies a pressing force in a direction, a rotation torque generating unit that is provided between the driving side member and the driven side member, and generates a rotation torque according to a rotation difference between the two members; Provided between the generating means and the clutch pressing member. A rotary linear motion converting means for converting the rotary torque generated in the rotary torque generating means into an axial movement of the clutch pressing member, wherein the rotary-linear motion converting means is generated in the rotary torque generating means. The gist of the configuration is that the linear motion amount with respect to the fluctuation amount of the rotational torque increases as the rotational torque increases when the rotational torque is small.

<Operation> According to the above-mentioned means, the rotation torque generating means generates the rotation torque in accordance with the rotation difference between the front and rear wheels, and the rotation-linear motion conversion means converts the rotation torque into the linear motion, and the clutch pressing member is operated. By moving in the axial direction, the pressing force of the clutch pressing member is applied to the friction clutch.

Further, since the rotation-linear motion conversion means is set to have a relationship in which the larger the rotation torque of the rotation torque generated by the rotation torque generation means is, the greater the linear motion amount with respect to the variation of the rotation torque is, When the rotation difference between the front and rear wheels is small, the increase in the differential limiting torque is small with respect to the increase in the rotation difference. Conversely, when the rotation difference between the front and rear wheels is large, the differential limiting torque due to the increase in the rotation difference is increased. The rate of increase of is rapidly increased.

<Example> An example of the present invention will be described below.

First Embodiment First, a first embodiment will be described with reference to FIGS.
It should be noted that this example is implemented on a propeller shaft of a four-wheel drive vehicle. In FIG. 1, which is a sectional view showing a front and rear wheel rotation absorbing device of a four-wheel drive vehicle, a companion is provided to a drive pinion 3 of a rear wheel side final reduction gear 2 to which power is transmitted from a propeller shaft 1 of the four-wheel drive vehicle. The flange 4 is spline-fitted and fixed by a fixing nut 5.

A cylindrical case 6 is attached to the companion flange 4 with attachment bolts 7.

A drive shaft 8 is rotatably supported in the case 6 via a bearing 9. The propeller shaft 1 is coupled to the tip end portion (left end portion in the drawing) of the drive shaft 8 by a bolt or the like. The tip of the drive shaft 8 is rotatably supported by the companion flange 4 via a bearing 10. In this example, the drive shaft 8 corresponds to the driving side member of the power transmission system for the front and rear wheels, and the case 6 and the companion flange 4 correspond to the driven side member.

A friction clutch 11 is disposed between the case 6 and the drive shaft 8 to generate a differential limiting torque that limits the differential between the members 6 and 8 in accordance with the pressing force in the axial direction. The friction clutch 11 includes a plurality of thrust washers 12 spline-fitted to the inner peripheral surface of the case 6, and a drive shaft 8
And a plurality of clutch plates 13 spline-fitted to the outer peripheral surface of the are alternately assembled.

The first cam member 14 adjacent to the front side (left side in FIG. 1) of the friction clutch 11 is spline-fitted to the inner peripheral surface of the case 6 and rotates integrally with the case 6. The cam member 14 has a ring shape. The first cam member 14 corresponds to the clutch pressing member according to the present invention.

An annular second cam member 15, which is meshed with the first cam member 14 via cam teeth 16 and 17 described later, is rotatably fitted in the case 6. First cam member
As shown in FIG. 2, cam teeth 16 and 17 are formed on the opposing surfaces of 14 and the second cam member 15, respectively, and both cam teeth 16 and 17 mesh with each other during non-differential rotation. Are integrally rotated, and at the time of differential rotation, meshing occurs due to sliding, that is, a phase shift of the cam teeth 16 and 17 occurs, and a cam reaction force in opposite directions occurs. The cam reaction force acting on the second cam member 15 is received by the snap ring 18 attached to the inner peripheral surface of the case 6, and the cam reaction force acting on the first cam member 14 is frictional. It acts as a pressing force against the friction plate composed of the thrust washer 12 and the clutch plate 13 of the clutch 11, and is received by the end face of the companion flange 4.

As shown in FIGS. 2 to 4, the shape of the cam teeth 16 and 17 of the cam members 14 and 15 has a gentle wave shape having alternating peaks A and valleys B. . Thus, the cam teeth 16 and 17 are, as shown in FIGS. 5 and 6,
The shape is set such that the pressure angle increases as it approaches the tooth tip a. That is, if the pressure angle on the valley B side of each cam tooth 16, 17 is θ ₁ and the pressure angle on the crest A side is θ ₂ , then θ ₁ <θ ₂
Are set so that

Further, as shown in FIG. 1, a viscous coupling is provided between the second cam member 15 and the drive shaft 8.
19 are provided. As is well known, the viscous coupling 19 is a case in which a highly viscous silicone oil is filled in a case that is sealed by an inner case 20 and an outer case 21, and a plurality of sheets are spline-fitted to the inner case 20. An inner plate (reference numeral omitted) and a plurality of outer plates (reference numeral omitted) that are spline-fitted to the outer case 21 are alternately assembled. Then, the inner case 20 is spline-fitted with the drive shaft 8 and integrally rotated, and the outer case 21 is spline-fitted with the second cam member 15 and integrally rotated. The viscous coupling 19 corresponds to the rotating torque generating means in the present invention. The cam mechanism composed of the cam teeth 16 and 17 corresponds to the rotary-linear motion converting means in the present invention.

In the front and rear wheel rotation absorbing device for a four-wheel drive vehicle described above, for example, when a vehicle wheel slips on a road surface having a low coefficient of friction, such as on a snowy road, there is a difference in rotation between the front wheel and the rear wheel. Occur. Then, differential rotation occurs between the propeller shaft 1 and the drive pinion 3 of the final reduction gear 2.

In this case, the inner case 20 of the viscous coupling 19 rotates together with the drive shaft 8, while the outer case
21 rotates together with the drive pinion 3 via the companion flange 4, the case 6, the first cam member 14, and the second cam member 15, so that the viscous coupling 19 eventually has the inner case 20 and the outer case 21. A difference in rotation occurs between the two, and viscous friction torque proportional to the difference in rotation is generated.

The viscous friction torque of the viscous coupling 19 is first transmitted to the second cam member 15. Then, both cam teeth 16 and 1 of the first cam member 14 and the second cam member 15 which have been integrally rotated until the viscous friction torque is generated.
During the period between 7, both cam members 1 due to the viscous friction torque.
Relative rotation occurs between 4 and 15, and cam reaction force (thrust force) is generated by both cam teeth 16 and 17. As a result, the first cam member 14 slides in the direction away from the second cam member 15 (rightward in FIG. 1), and the friction clutch 13
Generates frictional force on. That is, the viscous friction torque causes a cam reaction force between the cam members 14 and 15,
By the cam reaction force acting on the friction clutch 13,
A frictional force is generated between the thrust washer 12 of the friction clutch 13 and the clutch plate 13, and this frictional force acts as a differential limiting torque between the propeller shaft 1 and the drive pinion 3, so that the differential limiting torque is It is approximately proportional to the rotation difference between the propeller shaft 1 and the drive pinion 3.

Therefore, a small viscous friction torque of the viscous coupling 19 is caused by the cam action of both cam members 14 and 15,
Since a large thrust force proportional to the rotation difference is generated and the thrust force is applied as a large pressing force to the friction clutch 11, a large differential limiting torque is obtained and a large driving force transmission torque is obtained. The driving force from the propeller shaft 1 is transmitted to the drive pinion 3 of the final reduction gear device 2 via this driving force transmission torque.

Since the cam teeth 16 and 17 of both cam members 14 and 15 are set to have a shape in which the pressure angle increases as they come closer to the tooth tip a, the differential limiting torque of the friction clutch 11 causes the front and rear wheels to rotate. The smaller the difference, the smaller the increase in the differential limiting torque due to the increase in the rotation difference, and the larger the difference in rotation, the larger the increase in the differential limiting torque with the increase in the rotation difference. The relationship between the rotation difference and the differential limiting torque is shown in FIG.

For this reason, during normal turning and the like, since the rotation difference between the front and rear wheels is small, the viscous friction torque of the viscous coupling 19, the cam reaction force acting on the friction clutch 11, and the friction limit torque of the friction clutch 11 are also small. Thrust washer 12 and clutch plate 13 of the friction clutch 11.
The difference in rotation between the front and rear wheels is favorably absorbed by the difference in rotation between the front and rear wheels, and the tight corner braking phenomenon is suppressed or so-called mitigated. In addition, when the rotation difference between the front and rear wheels becomes large, the increase in the rotation difference also increases the differential limiting torque of the friction clutch 11, and a large driving force is obtained.

In this way, according to the front and rear wheel rotation absorbing device, ideal absorption of the rotation difference between the front and rear wheels and transmission of the driving force can be achieved in accordance with the vehicle requirements.

The differential limiting torque when the rotation difference between the front and rear wheels is small and large is expressed by the following equation. That is, the differential limiting torque T ₁ when the rotation difference is small (during low rotation) is represented by T ₁ = (T ₀₁ / R ₀ ) × tan θ ₁ × n × μ × R.
Further, the differential limiting torque T ₂ when the rotation difference is large (at the time of high rotation) is represented by T ₂ = (T ₀₂ / R ₀ ) × tan θ ₂ × n × μ × R.

In the above formula, T ₀₁ is the viscous torque of the viscous coupling 19 at low rotation, R ₀ is the effective radius of the cam, θ ₁ is the pressure angle of the cam teeth at low rotation, n is the number of friction surfaces of the friction clutch 11, μ is the friction coefficient of the friction plate of the friction clutch 11, R is the effective radius of the friction plate, T ₀₂ is the viscous torque of the viscous coupling at high rotation, and θ ₂ is the pressure angle of the cam teeth at high rotation.

Second Example Next, a second example will be described. It should be noted that this example is incorporated in a rear wheel side final reduction gear of a four-wheel drive vehicle.

As is well known, in FIG. 8 showing the final reduction gear in a sectional view, a differential case 27 is rotatably supported in a differential carrier 26 of the final reduction gear 25 via a bearing 28.

A ring gear 29 is attached to the outside of the differential case 27 with a fixing bolt 30.
Installed by The ring gear 29 meshes with a drive pinion 31 connected to a propeller shaft (not shown), and the driving force from the drive source is input to the ring gear 29 via the drive pinion 31.

In the differential case 27, a differential pinion 33 rotatably supported via a pinion shaft 32, and a differential pinion 33.
A differential gear train consisting of left and right side gears 34, 35 meshing with is incorporated.

A side gear shaft 36 is coupled to the right side gear 35. An axle shaft that transmits power to the right drive wheel (not shown) is coupled to the side gear shaft 36. The left side gear 34 has a side gear shaft.
37 is connected via the front and rear wheel rotation absorbing device described later.
An axle shaft that transmits power to the left drive wheel (not shown) is coupled to the side gear shaft 37. Therefore, the drive force input to the ring gear 29 is transmitted to both axle shafts via the differential gear train, and both drive wheels are rotated. When a difference in rotation occurs between the left and right drive wheels, both side gears 34, 35 rotate differentially, and at the same time, relative rotation occurs between the side gears 34, 35 and the differential case 27.

The left side gear 34 is the side gear shaft.
It is rotatably supported by 37 via a needle roller bearing 38. Then, between the side gear 34 and the side gear shaft 37, the front and rear wheel rotation absorbing device similar to that of the first embodiment is installed in substantially the same manner. In addition, in the second embodiment, the side gear 34 replaces the companion flange 4 and the case 6 of the first embodiment, and the side gear shaft 37 replaces the drive shaft 8 of the first embodiment. Since it is almost the same as the example, the same parts are designated by the same reference numerals and the description thereof is omitted. In this example, the side gear 34 corresponds to the driving side member of the power transmission system for the front and rear wheels, and the side gear shaft 37 corresponds to the driven side member.

Also according to this embodiment, substantially the same operational effects as those of the first embodiment can be obtained. It should be noted that the front and rear wheel rotation absorbing device of this example has a side gear 34 and a side gear shaft 37 due to the difference in rotation between the front and rear wheels.
A differential limiting torque is generated based on the rotation difference between and.

In this embodiment, the front and rear wheel rotation absorbing device is the final reduction device 25.
By incorporating it on the side gear shaft 37 of
It is advantageous from the aspect of H (general term for vehicle vibration noise phenomenon) and strength. That is, since the power from the propeller shaft is decelerated and transmitted to the side gear shaft 37, the side gear shaft 37 has a slower rotation speed than the propeller shaft, which causes the viscous coupling 19 and the friction clutch 11 to rotate.
It is possible to downsize the components such as, therefore, it can be said that the structure is advantageous for NVH and strength.

<Effect of the Invention> That is, according to the present invention, due to the difference in rotation between the front and rear wheels, the rotational torque generated by the rotational torque generating means is applied to the friction clutch as a large pressing force via the rotational-linear motion converting means. Unlike the device, a large differential limiting torque can be generated in the friction clutch, and a large driving force can be transmitted.

Further, since the rotation-linear motion conversion means is set to have a relationship in which the larger the rotation torque of the rotation torque generated by the rotation torque generation means is, the greater the linear motion amount with respect to the variation of the rotation torque is, When the rotation difference between the front and rear wheels is small, the increase range of the differential limiting torque is reduced with respect to the increase in the rotation difference, and the tight corner braking phenomenon can be suppressed by properly absorbing the rotation difference between the front and rear wheels. In addition, when the rotation difference between the front and rear wheels becomes large, the increase range of the differential limiting torque is rapidly increased with the increase in the rotation difference, and a large driving force can be transmitted by increasing the restraining force of the rotation of the front and rear wheels. Therefore, unlike conventional devices,
It is possible to satisfy both the suppression of the tight corner braking phenomenon corresponding to the requirements of the vehicle and the transmission of a large driving force.

[Brief description of drawings]

1 to 7 show a first embodiment of the present invention. FIG. 1 is a sectional view of a front and rear wheel rotation absorbing device of a four-wheel drive vehicle, FIG. 2 is a side view of a cam member, and FIG. FIG. 6 is a front view of the cam teeth of the second cam member, FIG. 4 is a front view of the cam teeth of the first cam member, and FIG. 5 is an explanatory view showing the meshing relationship of the cam teeth during low rotation, and FIG. FIG. 7 is an explanatory diagram showing the meshing relationship of the cam teeth during high rotation, and FIG. 7 is a characteristic diagram showing the relationship between the rotation difference between the front and rear wheels and the differential limiting torque. FIG. 8 is a sectional view of the final reduction gear of a four-wheel drive vehicle showing the second embodiment of the present invention. Further, FIG. 9 is a characteristic diagram showing the relationship between the rotation difference between the front and rear wheels and the differential limiting torque in the conventional device. 6 ... Case 8 ... Shaft 11 ... Friction clutch 14 ... First cam member 15 ... Second cam member 19 ... Viscous coupling

Claims (1)

[Scope of utility model registration request] 1. A front and rear wheel rotation absorbing device for a four-wheel drive vehicle, which is interposed in a part of a power transmission system of front and rear wheels of a four-wheel drive vehicle to absorb a rotational difference between a front wheel and a rear wheel. A friction clutch that is provided between the driving side member and the driven side member of the transmission system, and that generates a differential limiting torque that limits the differential between the two members according to the pressing force in the axial direction, and the driving side member. A clutch pressing member that is provided movably in the axial direction on either member of the driven side member and that applies a pressing force in the axial direction to the friction clutch, and is provided between the driving side member and the driven side member, Rotation torque generating means for generating a rotation torque according to a rotation difference between both members, and a rotation torque generated in the rotation torque generating means, which is provided between the rotation torque generating means and the clutch pressing member, is applied to the clutch pressing means. Time to convert to axial movement of member A rotational-linear motion conversion means, wherein the rotational-linear motion conversion means has a linear motion amount with respect to a variation of the rotational torque as the rotational torque is larger than when the rotational torque generated in the rotational torque generating means is small. The front and rear wheel rotation absorbing device of the four-wheel drive vehicle is characterized in that the relationship is set to increase.